The top U.S. military officer says there are indications Pakistan's intelligence service is still helping al-Qaida and Taliban militants in the country's tribal areas, along the Afghan border, and he says that must change. And another senior U.S. official indicated Friday that substantial new U.S. aid to Pakistan is contingent on such a change.

The Chairman of the Joint Chiefs of Staff, Admiral Mike Mullen, told CNN the strategic approach of Pakistan's intelligence services must change, and its members must stop supporting militants. Numerous experts and media reports have accused the service of supporting the militants, but Pakistani leaders have said they now recognize the threat those groups pose to Pakistan itself.

In many trips to Pakistan during the past year, Admiral Mullen has had a key role in trying to convince the country's leaders that the threat they face from extremists in their north and west, along the Afghan border, is at least as significant as the threat they see from India to the south and east.

He said on CNN at least some members of the intelligence service are not convinced. But the admiral told reporters in his office earlier Friday that Pakistani leaders do recognize the threat, although they do not necessarily see it the same way U.S. officials do. "My overall view on that is yes, they do. We sometimes differ on timelines and on priorities. But yes, absolutely," he said.

And the admiral says while problems persist in the Pakistani intelligence service, there have been improvements in the performance of the Frontier Corps, which is responsible for border security, and more activity in the border area by the Pakistani Army. "They've moved dramatically over the last seven, eight months with their Frontier Corps, who's had a big impact, and they've done pretty well. I would hope and want that kind of both leadership and focus to continue," he said.

Another senior U.S. official says such movement is necessary if Pakistan wants to get $1.5 billion of new U.S. aid each year for the next five years -- a key element of the new strategy President Obama announced on Friday. The Under Secretary of Defense for Policy, Michele Flournoy, was one of he top officials on the Obama strategy review team. The final document makes Pakistan a key element in a regional approach to reaching the president's main goal, the defeat of militant groups based in its northwestern region. "Part of doing that is, first of all, providing assistance at a level that is meaningful, but also ensuring that they understand that our ability to provide that assistance depends on seeing changes in past behaviors," he said.

While the administration of former-President George W. Bush also worked with Pakistan to fight militants who use its tribal areas as safe havens, Obama Administration officials say the enhanced regional approach is a key new aspect of their strategy.

Admiral Mullen says the effort to increase Pakistan's involvement in the fight against the terrorists is made more difficult by past problems in the U.S.-Pakistan relationship. "There's a trust deficit between the two countries, certainly between the two militaries that's been there. We sanctioned them for 12 years. We're starting to come out of it, but it's going to take some time," he said.

Admiral Mullen says it is significant that President Obama is asking the congress for five years of aid to Pakistan because that sends a message that the United States plans to support the country for years to come, as long as its leaders and security services are willing to help fight the terrorists.